Are patterns of genetic variation associated with morphological differences in River Red Gum?

Supervisor: Penny Butcher

Introduction

Eucalyptus camaldulensis Dehnh. (river red gum) is the only eucalypt which occurs in all mainland states of Australia. It is also one of the most widely planted eucalypts in temperate and tropical regions throughout the world. It is grown for a range of uses including fuelwood, paper pulp, construction timber, amenity plantings and land rehabilitation. Within Australia, it a key species for revegetation, particularly in areas affected by rising water tables and salinity.

Eucalyptus camaldulensis occupies a narrow ecological niche being confined to watercourses. Its ability to access water from drainage systems has enabled it to adapt to climatic conditions throughout most of the continent. Significant differences among provenances in morphological and quantitative traits have raised questions about whether patterns of genetic variation can be detected and whether variation is linked to environmental parameters.

Several infraspecific taxa have been described based on the complex pattern of morphological variation. However the geographical extent of these taxa has been poorly documented. Five main variants are often recognised:

var. camaldulensis – occurs mainly in temperate regions of the Murray-Darling Basin in south-eastern Australia;
var. obtusa – represents the tropical form, considered widespread throughout much of northern Australia;
subsp. simulata – occurs in north-east Queensland and has characters intermediate between var. obtusa and its close relative E. tereticornis;
var. subcinerea – a poorly documented arid zone variant described from Silverton near Broken Hill, NSW – recent field observations suggest that it is far more widespread and occurs throughout the Finke Drainage Basin; and
var. acuminata – occurs mainly in Queensland along the upper reaches of the Murray- Darling Basin and has morphological affinities with E. tereticornis.

Aims

The aim of this study is to determine whether differences in molecular variation can be detected between infraspecific taxa in E. camaldulensis.

Methodology

Leaf samples have been collected from ten individuals in populations from throughout the species geographic range. The project will involve an introductory study of variation in morphological traits using herbarium specimens from populations representing the five infraspecific taxa. Highly variable DNA markers (microsatellites) will then be used to determine if differences in molecular variation can be detected between morphological variants. The molecular component involves extraction of DNA from leaves collected from ten trees in each of four populations representing the five variants. DNA will be amplified by polymerase chain reaction (PCR) with microsatellite primers and an automated sequencer used to separate DNA fragments. Data will be analysed using standard statistical software packages for population genetic analysis. The student will present results from the study in a report and seminar.

Outcomes

By the end of the study the student will have gained experience in DNA extraction techniques, microsatellite analysis and assessment of morphological characters used to differentiate eucalypt taxa. They will also gain some background on how molecular techniques can assist in clarifying patterns of variation within a species complex.

Supervisors

Project supervisor: Penny Butcher (CSIRO FFP).

Taxonomic advisor: Maurice McDonald (CSIRO FFP).

Location

CSIRO Forestry and Forest Products
Australian Tree Seed Centre
Banks Street, Yarralumla
PO Box E4008
Kingston ACT 2604

Background reading:

Blakely WF (1955) ‘A key to the eucalypts, with descriptions of 522 species and 150 varieties’. 2nd edn. (Forestry and Timber Bureau: Canberra)

Brooker MIH, Kleinig DA (1999) ‘Field guide to eucalypts: Vol. 1. South-western and Southern Australia’. Revised Edition. (Bloomings Books: Melbourne)

Butcher PA, Otero A, McDonald, MW, Moran GF (2001). Nuclear RFLP variation in Eucalyptus camaldulensis Dehnh. from northern Australia. Heredity 88: 402-412.

Summer Scholarships 2003-2004

Are patterns of genetic variation associated with morphological differences in River Red Gum?